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Author Topic: Fixing a color cast  (Read 25378 times)

cmpentecost

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Fixing a color cast
« on: April 21, 2008, 10:02:57 AM »
This suggestion comes from Tim Grey, who is a Photoshop Guru and he works for Microsoft.  I've been subscribing to Tim Grey's emails for a couple of years, and have learned a lot from him.  His daily emails are free, and he covers one question and answer a day.  Most of the emails pertain to Photoshop or camera questions.  His website is www.timgrey.com.  Anyway, I have yet to try this technique, so I'll be anxious to see how it works.  If someone tries it out, it would be great if you could post the before and after photos for us to see.  Here it is:

When I was at Photoshop World in Orlando I saw you present a cool technique for fixing really bad color casts in an image, but I missed part of it. Can you remind me of the steps involved?

==========

Absolutely. This techniques comes across as being pure magic (which is why I like to present it!), and it can be incredibly helpful when you have an extreme color cast. This can happen with digital captures when the color temperature is set to a wrong value, but usually this degree of color cast comes from things such as old color photos that have become faded or otherwise shifted in color with time.

The first step is to create a copy of the Background image layer by dragging that layer to the Create a New Layer button at the bottom of the Layers palette. Then you need to determine the color of the color cast so you can compensate for it. To do so, select Filter > Blur > Average from the menu. This will convert this layer to a single color that represents the average color of all pixels in the image. Of course, this is the problem color, so you need to determine the opposite of it so you can apply it as a compensation for the color cast. To determine that opposite color, select Image > Adjustments > Invert from the menu. This will convert the layer to the opposite of the average layer, which means it is the opposite of the color cast.

To apply this color to the underlying image, set the blend mode to Color using the dropdown at the top-left of the Layers palette. This blend mode will cause the layer to alter only the color of the underlying image, completely offsetting the strong color cast. The problem is, this will result in too strong an effect, with a color cast that is the opposite of the original, but much stronger. To tone things down and produce an image without a color cast, simply reduce the Opacity using the slider at the top-right of the Layers palette. Adjust the value until you have a perfectly neutral color in the image.

The final result will represent relatively accurate color, but it will probably appear a bit flat and possibly lacking saturation. To compensate for this you'll need to boost saturation (using a Hue/Saturation adjustment layer) and contrast (using Levels or Curves).


Offline kiska

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    • ob
Re: Fixing a color cast
« Reply #1 on: April 21, 2008, 11:23:43 AM »
Here ya go, Missy!

kiska
Photoshop CS5, MacPro

cmpentecost

  • Guest
Re: Fixing a color cast
« Reply #2 on: April 21, 2008, 11:37:46 AM »
Wow!  Not bad!  Thanks Kiska!

Chris

Offline schen

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Re: Fixing a color cast
« Reply #3 on: April 21, 2008, 11:47:39 AM »
This method may provide a quick fix as shown in the middle frame below but is not a substitute for manual adjustments (right frame).

Windows 7, Photoshop CS5

cmpentecost

  • Guest
Re: Fixing a color cast
« Reply #4 on: April 21, 2008, 11:59:00 AM »
I found a photo amongst some of our OPR damaged photos and tried it also:



Offline kiska

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    • ob
Re: Fixing a color cast
« Reply #5 on: April 21, 2008, 12:04:50 PM »
It seems to work best on a yellow cast.
kiska
Photoshop CS5, MacPro

Offline Hannie

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Re: Fixing a color cast
« Reply #6 on: April 21, 2008, 02:46:02 PM »
Thanks for sharing this Chris!
I tried it out on several photos and it works well, sometimes the adjustments made the "conventional way come out better.  That may have to do with poor sat/contr adjustment on my side after using Tim's method.
In the examples below from left to right:
 
   original,     Tim's method,    "normal"method (levels etc.)

Hannie

 



Hannie Scheltema
Distribution Coordinator
hannie@operationphotorescue.org

mschonher

  • Guest
Re: Fixing a color cast
« Reply #7 on: April 21, 2008, 07:33:25 PM »
 Hi Chris; AKA Snow Bunny,

I used this technique for the first time today and I love it.  Thanks for posting this method, it's fast and easy.

PS  are you keeping busy shoveling the white fluffy stuff?   :P

Mary

cmpentecost

  • Guest
Re: Fixing a color cast
« Reply #8 on: April 21, 2008, 08:05:27 PM »
Hi Mary,

I'll be the first to say I am VERY ready for Spring, and perhaps I did my snow dance just a bit too hard this winter.  My daffodils started to come up and I even had one blossoming, but I checked it today, and it was lying on the ground, dead.  April is the hardest month of the year in Montana.  I love it out here May through March, but April just doesn't want to give up winter.

I'm glad this technique worked.  Definitely one to keep in a list of favorites.

Chris